tp 外连接查询

$villages = M('houseVillage')
    ->alias('a')
    ->where($map)
    ->join("RIGHT JOIN " . C('DB_PREFIX') . "dwz_admin_member as b ON a.village_id = b.village_id")
    ->group("a.village_id")
    ->field('a.village_id,a.village_name')
    ->order("village_id desc")
    ->select();